What kind are you looking for?
If its action/adventure then anything by Alastair Reynolds is good, or Altered Carbon by richard morgan is also good, but Richard Morgan's books get pretty samey after a while and there are a couple of science plot holes which irritate me a bit...

If its the more detailed future gazing sort of stuff (which i would say asimov kind of falls into) then i think arthur c clarke books or 'Red Mars' by Kim Stanley Robinson. Red mars is enjoyable and educational at the same time, the author seriously knows his shit about how colonising mars could work.

Enders game by Orson Scott Card is a good book, its almost more psychological fiction than science fiction but has some nice space combat theory stuff.

Thats all that springs to mind for the moment (probably because its whats sitting on my shelf : If you get stuck for more books you can just look at the lists of books that have won hugo and nebula awards for ideas. I think most of the ones i've mentioned above probably won awards, but thats mostly coincidence.

Oh My.....there are so many great SCFI authors, do you like the modern writers or the the ones from the last 30 years or so,
Hmmmmm Lester Del Ray, Jack Chalker, Phil Hogan, For Great Military SCFI then, Ringo, Flint, Webber, Drake,
Go the Baen.com site and they have a ton of free Downloads and many of the authors named above have granted free access to some of their work. I could name more but if you hit their site you can browse and see how they classify the Authors.

i'll second iain m banks especially 'the player of games' and 'Consider Philebas' or if you're looking for something a bit more twisted 'Use of Weapons'

and I'll second the original dune book too (i didn't like the rest of them though)

He's bringing a new "culture" book out in february I think. Can't wait

cheers for the heads up, sounds a little unusual

In a world renowned within a galaxy full of wonders, a crime within a war. For one brother it means a desperate flight, and a search for the one - maybe two - people who could clear his name. For his brother it means a life lived under constant threat of treachery and murder. And for their sister, it means returning to a place she’d thought abandoned forever.

Only the sister is not what she once was; Djan Seriy Anaplian has become an agent of the Culture’s Special Circumstances section, charged with high-level interference in civilisations throughout the greater galaxy.

Concealing her new identity - and her particular set of abilities - might be a dangerous strategy. In the world to which Anaplian returns, nothing is quite as it seems; and determining the appropriate level of interference in someone else’s war is never a simple matter.

Banks tells me that he has spent the past three months writing another Culture novel. It will be called Matter and is to be published next February. "It's a real shelf-breaker," he says enthusiastically. "It's 204,000 words long [544 pages, according to Amazon] and the last 4,000 consist of appendices and glossaries. It's so complicated that even in its complexity it's complex. I'm not sure the publishers will go for the appendices, but readers will need them. It's filled with neologisms and characters who disappear for 150 pages and come back, with lots of flashbacks and -forwards. And the story involves different civilisations at different stages of technological evolution. There's even one group who have disappeared up their own fundaments into non-matter-based societies". [1]